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Home > Archive > Voice over IP Cisco > April 2006 > COS on Cisco 3750 - help please
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COS on Cisco 3750 - help please
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| Group, Russ 2006-04-20, 6:57 pm |
| Hi all
I'm having a problem with voice quality going over the WAN. We use a
2801 on each end. Someone suggested that there might be a issue with
COS. I thought by default cisco tags all voice traffic as COS 5. AT&T
is looking for COS 1. Am I wrong about cisco being tagged as COS 5? If
not, then how do I change the 3750 to tag the voice as COS 1 to match
AT&T?
Thanks
Russ
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| Scott O'Donnell 2006-04-20, 6:57 pm |
| You could use a service policy inbound on the ethernet interface of the
2801 to remark IP Phone traffic to any value AT&T wants.
I would imagine they would be asking for a Layer 3 DSCP value though,
not a layer 2 COS value to be set.
What type of hand off is AT&T providing?
________________________________
From: cisco-voip-bounces@puck.nether.net
[mailto:cisco-voip-bounces@puck.nether.net] On Behalf Of Group, Russ
Sent: Thursday, April 20, 2006 5:00 PM
To: cisco-voip@puck.nether.net
Subject: [cisco-voip] COS on cisco 3750 - help please
Hi all
I'm having a problem with voice quality going over the WAN. We use a
2801 on each end. Someone suggested that there might be a issue with
COS. I thought by default cisco tags all voice traffic as COS 5. AT&T
is looking for COS 1. Am I wrong about cisco being tagged as COS 5? If
not, then how do I change the 3750 to tag the voice as COS 1 to match
AT&T?
Thanks
Russ
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| Jonathan Charles 2006-04-20, 6:57 pm |
| The RTP Stream (the actual voice traffic) is labeled COS 5 (or DSCP
EF) and the Control traffic (SCCP, MGCP, etc) is labeled COS 3 (DSCP
AF31) by the phone.
By default switches remark all DSCP (and COS) to 0 unless they are
Cisco switches set to trust the phone's DSCP settings.
So, if you have cisco switches, the traffic should be marked correctly already.
The next step is to do something with it... and the thing to do is
creating a service policy on the router (CBWFQ).
Now, since AT&T wants it tagged as COS 1 (which I cannot, for the life
of me, figure out why), the only way to do that would be to follow
Scott's recommendation and place another service policy on the ingress
of the router to remark to COS 1.
J
On 4/20/06, Group, Russ <rgroup@harman.com> wrote:
>
>
> Hi all
>
> I'm having a problem with voice quality going over the WAN. We use a 2801
> on each end. Someone suggested that there might be a issue with COS. I
> thought by default cisco tags all voice traffic as COS 5. AT&T is looking
> for COS 1. Am I wrong about cisco being tagged as COS 5? If not, then how
> do I change the 3750 to tag the voice as COS 1 to match AT&T?
>
> Thanks
>
> Russ
>
> ________________________________________
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> cisco-voip mailing list
> cisco-voip@puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-voip
>
>
>
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